Sodom and Gomorrah IV pp 515-42

p 520-22 | Émile Boutroux (1845–1921), eminent 19th century French philosopher of science & religion, and an historian of philosophy. Firmly opposed to materialism in science, he was a spiritual philosopher who defended the idea that religion and science are compatible, at a time when the power of science was rising inexorably. His work is somewhat overshadowed by Henri Bergson. Elected to the Academy of Moral & Political Sciences (1898) & the Académie française (1912). Henri Bergson (1859–1941), major French philosopher, convinced many that immediate experience & intuition are more significant than abstract rationalism & science for understanding reality. He was awarded the 1927 Nobel Prize in Literature and in 1930, France awarded him its highest honour, the Grand-Croix de la Legion d'honneur. (wiki) 
p 521 | "like a dulcimer" refers to a couplet from Baudelaire's Fleurs du mal: "Your memory, like uncertain fables, / Wearies the reader like a dulcimer." (Sturrock)

p 521 | Porphyry of Tyre (c. 234–c. 305 AD) was a Neoplatonic philosopher who edited & published the Enneads, the only collection of the work of his teacher Plotinus. Plotinus (c.204/5 – 270) was a major philosopher of the ancient world. His teacher was Ammonius Saccas & he is of the Platonic tradition. Historians of the 19th century invented the term Neoplatonism and applied it to him & his philosophy, which was influential in Late Antiquity. Much of his biographical information comes from Porphyry's preface to the Enneads. (wiki)

p 525 | toquewoman's small hat without a brim made in any of various soft close-fitting shapes. Here are some outfits made for motoring

p 524 | Footman.

p 524-25  | "Prosper, dear hope ...": a line from Racine's Esther, wrongly attributed here to Athalie. In French, "Prospérez, cher espoir d'une nation sainte." "Come, come, my daughters": "Venez, venez, mes filles."  They must be summoned": "il faut les appeler."

p 527 | Euryclea: In the Odyssey, when Ulysses returns to Ithaca in disguise, his nurse Euryclea recognizes him by a scar on his foot or leg.

p 528 | "... faulty restorations at Notre-Dame" refers to the restorations done by Viollet-le-Duc and others between 1844 and 1864. (Sturrock) Also see this excerpt about church painting & restorations.

p 528 | "...those objects . . . mantelpiece:" a reference to Edgar Allan Poe's story "The Purloined Letter," translated into French by Baudelaire, in which a much-sought incriminating letter lies unconcealed. Text is here. (Sturrock)

p 528 | Etruscan

p 534 | Epreville
p 535 | The Okeanides (or Oceanides) were 3000 goddess Nymphs who presided over the sources of earth's fresh-water, ranging from rainclouds to subterranean springs and fountains.

p 538 | Montsurvent

p 541 | Hadrian (d. 138 CE), 14th Emperor of Rome, built the Pantheon in Rome and Hadrian’s Wall in northern Britain.